This invention relates in general to planetary transmission systems and gearing and deals more particularly with an improved single-stage compound planetary gear system embodying such gearing.
Heretofore it has been general practice in the planetary transmission art to utilize multi-staging of a series of planetary gear sets where high ratios of speed change (greater than about 10:1) have been required. In special cases where size, weight and efficiency have not been critical, compound planetary gearing has been used in high gear ratio transmissions. Either approach has generally utilized involute gears or modified involute gear forms. In such transmission systems it has been the usual practice to utilize wide gears, that is gears wherein the ratio of the face width to pitch diameter (F/D) is greater than 1 to compensate for high Hertzian stresses encountered in high-ratio meshes. This approach has been generally preferred to the use of relatively large diameter gears to maintain proper design stress limits on gear teeth and bearings. However, such wide gears are usually relatively heavy and tend to produce more severe load gradients across the tooth faces due to axial misalignments between meshing gears. Self-aligning mechanisms have been utilized such as floating, spline members, cams, and flexing type mechanisms to overcome this problem, however, the provision of such special support structures add substantially to the cost and complexity of a transmission system.
The present invention is concerned with the aforesaid problems. Specifically, it is the general aim of the invention to provide an improved single-stage compound planetary gear system which utilizes improved gearing whereby a broad range of high-gear ratios can be attained in a relatively simple transmission system utilizing gears having low face width to pitch diameter ratios (F/D less than 1.0).